The gold precipitant particle size will depend more on how easily the newly reduced gold atoms can come into contact with each other to form clumps of gold atoms heavy enough to sink to the bottom as they overcome the resistance of the solution to gravity.
precipitated gold is normally tan to brownish if precipitated from a solution loaded with base metals the gold is usually dark brown to black.
The color of the solution should be fairly clear after precipitating gold from a fairly pure gold chloride solution, when base metals like copper and some other metals are involved they can leave some color to the solution after precipitation.
If tin is involved the gold can form colloids which can give the colors you mention to the solution...
Even if you had only pure gold in solution it is hard to use up all of the nitric, adding more gold will help to consume the remaining nitric but it would take many many days to consume all of the nitric this way, Strong heat can speed the process to a matter of hours.
If base metals are involved they can form nitrate salts in solution, here even if you consume all of the free nitric acids, later additions of HCl in the process will reform nitric acid in solution from the nitrates created.
We can see this when we evaporate the solution down to a very concentrated solution in an attempt to deNOx the solution, upon adding a little HCl to rewet for the next evaporation cycle we see a red cloud form from nitrate salts concentrated in solution.
nickvc said:
Welcome to the forum naandesh.
More details would help provide better answers such as what have you dissolved, how much and what volumes and ratios of acids.
Just leaving your aqua regia will not remove the nitric and depending on the information we need from above will help give you answers.
